1. Field of the Invention
This invention relates to a biochemical analysis method for applying a liquid sample to a long test film provided with a single reagent layer or a plurality of reagent layers, maintaining the long test film at a predetermined temperature (i.e. carrying out incubation) for a predetermined time, and measuring the optical density of the product formed by a reaction of a reagent in the reagent layer with the liquid sample during or after the incubation. This invention particularly relates to a biochemical analysis method enabling accurate measurement of the quantities of a products formed by reactions taking place on a long test film.
2. Description of the Prior Art
Qualitative or quantitative analysis of a specific chemical constituent in a liquid sample is generally conducted for various industrial purposes. Particularly, it is very important in biochemical and clinical fields to quantitatively analyze chemical constituents or physical constituents in body fluid such as blood or urine.
Recently, as disclosed in, for example, Japanese Patent Publication No. 53(1978)-21677 and Japanese Unexamined Patent Publication No. 55(1980)-164356, a dry type chemical analysis slide was developed for use in a system for quantitatively analyzing a specific chemical constituent or a specific physical constituent contained in a liquid sample simply by applying a droplet of the liquid sample to the slide. With a method using the chemical analysis slide, it is possible to analyze a liquid sample more simply and more quickly than with a conventional wet type analysis method. Therefore, the use of the chemical analysis slide is desirable particularly in medical organizations, research laboratories, or the like where many samples are to be analyzed.
In order to analyze a chemical constituent or the like contained in a liquid sample by use of the chemical analysis slide, a measured amount of the liquid sample is put on the chemical analysis slide and is maintained at a predetermined temperature (i.e. incubated) for a predetermined time in an incubator to cause a color reaction. The chemical analysis slide is then exposed to light having a wavelength selected in advance, the selection of which wavelength depends on the constituents of the liquid sample and the constituents of a reagent contained in the reagent layer in the chemical analysis slide. Quantitative analysis of the chemical constituents or the like in a sample is carried out by irradiating a reaction product formed on a chemical analysis slide and finding the ratio of transmitted vs. reflected light.
In medical organizations, research laboratories or the like where many liquid samples are analyzed, it is desirable to conduct the analysis automatically and sequentially. To satisfy this need, various chemical analysis apparatuses have been proposed, which by use the aforesaid chemical analysis slides. One of such chemical analysis apparatuses is disclosed in, for example, Japanese Unexamined Patent Publication No. 56(1981)-77746. Also, as a means for analyzing liquid samples automatically and sequentially, an apparatus is proposed in, for example, U.S. Pat. No. 3,526,480 wherein a long tape-like test film containing a reagent is used instead of the aforesaid chemical analysis slides, and sample application, incubation and measurement are carried out sequentially on adjacent portions of the test film. The running cost of the apparatus using the long tape-like test film is lower than the running cost of the apparatus using the chemical analysis slides, and measurements on many liquid samples can be carried out sequentially by use of a simple mechanism.
The long test film may be wound around a feed reel, for example and then loaded into the apparatus. The long test film is affected by temperature or humidity and will deteriorate (i.e., the chemical properties of the long test film will change) if the temperature and humidity are not closely controlled. Accordingly, the applicant proposed a biochemical analysis apparatus provided with a refrigerator kept at a low temperature and low humidity for accommodating the long test film so that it does not deteriorate if a long time occurs between when a long test film is loaded into the apparatus and when analysis begins. At the time at which analysis is to be carried out with the proposed biochemical analysis apparatus, the long test film is pulled out of the refrigerator by a test film conveyance means until an edge of a specific desired portion of the test film is aligned with a predetermined sample applying position, after which a liquid sample is applied onto the long test film, and incubation and measurement are then carried out. Therefore, when a plurality of liquid samples are to be analyzed sequentially by use of the long test film, the length of the portion of the long test film, which is pulled out sequentially by the test film conveyance means equals the minimum length necessary for a single analysis. The long test film is forwarded just before each liquid sample is applied onto the long test film.
However, the place at which the film exits from the refrigerator and the sample applying position are spaced somewhat apart from each other. Therefore, when a plurality of liquid samples are to be analyzed by moving the long test film forward in the manner mentioned above, part of the long test film to which the present sample is to be applied is pulled out of the refrigerator when the sample analyzed immediately prior to the present sample is applied. Therefore, a part of the long test film is not kept at as low a temperature and at as low a humidity as the film portions still in the refrigerator. Accordingly, if analysis is interrupted and a long time elapses prior to the application of a next liquid sample, the part of the long test film positioned outside of the refrigerator, and onto which a liquid sample has not yet been applied, deteriorates, and an accurate analysis of a sample applied to a deteriorated film portion cannot be done.